Hi,
this relates to the question "How to set a former environment?" asked
yesterday. What is the best way to to return a function with a
minimal environment from a function? Here is a dummy example:
foo <- function(huge) {
scale <- mean(huge)
function(x) { scale * x }
}
fcn <- foo(1:10e5)
The problem with this approach is that the environment of 'fcn' does
not only hold 'scale' but also the memory consuming object 'huge',
i.e.
env <- environment(fcn)
ll(envir=env) # ll() from R.oo
# member data.class dimension object.size
# 1 huge numeric 1000000 4000028
# 2 scale numeric 1 36
save(env, file="temp.RData")
file.info("temp.RData")$size
# [1] 2007624
I generate quite a few of these and my 'huge' objects are of order
100Mb, and I want to keep memory usage as well as file sizes to a
minimum. What I do now, is to remove variable from the local
environment of 'foo' before returning, i.e.
foo2 <- function(huge) {
scale <- mean(huge)
rm(huge)
function(x) { scale * x }
}
fcn <- foo2(1:10e5)
env <- environment(fcn)
ll(envir=env)
# member data.class dimension object.size
# 1 scale numeric 1 36
save(env, file="temp.RData")
file.info("temp.RData")$size
# [1] 156
Since my "foo" functions are complicated and contains many local
variables, it becomes tedious to identify and remove all of them, so
instead I try:
foo3 <- function(huge) {
scale <- mean(huge);
env <- new.env();
assign("scale", scale, envir=env);
bar <- function(x) { scale * x };
environment(bar) <- env;
bar;
}
fcn <- foo3(1:10e5)
But,
env <- environment(fcn)
save(env, file="temp.RData");
file.info("temp.RData")$size
# [1] 2007720
When I try to set the parent environment of 'env' to emptyenv(), it
does not work, e.g.
fcn(2)
# Error in fcn(2) : attempt to apply non-function
but with the new.env(parent=baseenv()) it works fine. The "base"
environment has the empty environment as a parent. So, I try to do
the same myself, i.e. new.env(parent=new.env(parent=emptyenv())), but
once again I get
fcn(2)
# Error in fcn(2) : attempt to apply non-function
Apparently, I do not understand enough here. Please, enlighten me. In
the meantime I stick with foo2().
Best,
Henrik
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